The present invention relates to a dual-coil type CRT image tilt correcting device which uses two ring coils respectively charged to produce reversed magnetic fields for correcting the tilt angle of the electron beam without causing a convergence error.
In a normal monitor, a bias coil is energized by electric current of saw-tooth wave to produce a magnetic field for biasing the electron beam. Because the earth has a magnetic field, it will interfere with the magnetic field of the biased coil to affect the biasing of the electron beam. Further, the strength of the magnetic field of the earth varies with the locations, the tilt angle and convergence of the electron beam will be different when a standard monitor is used in different locations. Therefore, the magnetic ring of the biased coil must be properly adjusted. However, it is not easy to adjust the magnetic ring of the biased coil. Only an experienced professional person can do the job.